The symptom complex of bronchiolitis fibrosa obliterans, although fairly well defined, is one which usually escapes clinical recognition. This disease results from organization of fibrinous exudate in the bronchioles in response to local injury. The total number of cases reported is small, and only 1 has been discovered among the 42,038 autopsies performed by members of the pathology department at the University of Minnesota Medical School since 1899. In this case the patient was studied clinically at the Minneapolis General Hospital, and I followed closely the course of his disease. It is hoped that a review of this case and a resume of the literature may help to direct the attention of physicians to this disease when they are dealing with conditions having similar symptomatology. Bronchiolitis fibrosa obliterans was first described and recognized as a pathologic entity in 1901 by Lange,1 who differentiated between it and other processes which